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1. Field of the Invention
The apparatus of the present invention relates to an apparatus for injecting tubing down a pipeline, well or open hole. More particularly, the present invention relates to a bi-directional thruster pig apparatus which is capable of injecting coiled tubing down a pipe in deep water to provide service to the pipe in order to remove blockages such as paraffin, hydrates, scale or solid debris. The pipe in question may be part of a vertical or horizontal well, pipeline or a combination of both. More particularly, the apparatus and method of the present invention provides a bi-directional thrust system by using changeable, adjustable check valves that are double acting in each direction, the amount of hydraulic thrust pressure being set and predetermined prior to the job or changed in the fields. The bi-directional fluid flow feature of the apparatus allows the apparatus to be retrievable from the pipeline after it has completed its cleaning function by eliminating or reducing any hydraulic or hydrostatic force against the pig as it is retrieved from the pipeline or well.
2. General Background of the Invention
Drilling for and producing subterranean oil and gas deposits and seeking out other energy sources, it is necessary to drill either vertical, horizontal, curved or a combinations of such, and then to insert an elongated tube from the surface deep into a pipe or the open hole. Such drilled holes may be part of, for example, a well, pipe line, production line, or drill pipe, depending on the circumstances. Quite often it is necessary to insert a tube, whether it be continuous or segmented into the pipe or open hole, the tube having a diameter smaller than the diameter of the drill, production pipe or open hole, in order to remove or destroy blockages which have formed in the pipe or drilled hole.
It has become very beneficial in the cleaning or clearing of pipelines, or horizontal holes to utilize a continuous tubing, referred to as coiled tubing. The tubing is usually injected type tubing which is relatively flexible, and is of a continuous length being rolled off a large reel at the rig site and down hole. Various types of tools may be connected to the end of the coiled tubing to undertake whatever task is required below the surface. Coil tubing strings can be joined together up to and exceeding ten miles at a time.
Large forces are often necessary to insert and withdraw thousands of feet or more of steel tubing into a pipe or open hole which may be filled with hydrocarbons or other materials.
Most apparatuses focus on the injector head located where the smaller tubing is injected into the larger tubing. The injector head grips the tubing along its length and, in conjunction with a motor, guides and forces the tubing into the pipe via, for example, a dual, opposing gripper chain or conveyor belt on the surface of the well. Injector heads are quite common in the oil and gas art, as found, for example, in U.S. Pat. Nos. 3,827,487; 5,309,990; 4,585,061; 5,566,764; and 5,188,174, all of which are incorporated herein by reference.
A common problem found in the art of injecting coiled tubing down a pipeline is that the tubing may be bent or kinked, i.e., the tubing becomes helical, down the well due to the large forces pushing against it and the weight of the tubing itself. is Furthermore, as the pipe becomes more horizontal, the weight of the coiled tubing itself no longer acts as a force pulling the tubing along, and instead acts against the wall of the pipe, creating friction. In addition, the weight of the tube no longer acts to straighten the coiled tubing, and the coil encourages coiling in the pipe. Such a coil, coupled with friction, results in increased force between the coiled tube and the inner diameter of the pipe, and this effectively binds the tubing. As a result of this and other problems, such prior art devices cannot effectively insert more than about 3,000 to about 5,000 feet (900 to 1500 meters) of tubing in substantially horizontal pipe.
Other methods have been employed to increase the length to which tubing can be injected. U.S. Pat. No. 5,704,393, describes an apparatus that can be set in the well at the end of the coiled tubing string at a determinable location. The apparatus is a valve apparatus, a packer apparatus, and a connector. Seals are provided that allow the coiled tubing, but not fluid, to move in a centrally located bore through the packer apparatus. The apparatus is immobile against the outer pipeline, and has the ability to restrict or prevent fluid flow. Once the packer is set, the annular pressure, i.e., the pressure differential between the pipeline and the interior of the coiled tubing, is increased by injecting fluid into the annular volume. This increased pressure stiffens and straightens the coiled tubing, allowing for increased distance of injection of coiled tubing into the pipeline.
Further, U.S. Pat. No. 6,260,617 issued Jul. 17, 2001 entitled xe2x80x9cSkate Apparatus for Injecting Tubing Down Pipelines,xe2x80x9d teaches a device which is intermittently placed along the length of the coil tubing, and having a plurality of roller members which allows the coil tubing to be maintained within the center of the pipe in order to. reduce the friction between the coil tubing and the pipeline. However, over large distances over two or more miles, such a device is still not suitable.
All of the aforesaid problems confronted in the art of using coiled tubing down a borehole or pipeline can be found in related U.S. Pat. No. 6,315,498, entitled xe2x80x9cThruster Pig Apparatus For Injecting Tubing Down Pipelines,xe2x80x9d which is incorporated herein by reference. This patent discloses a method and apparatus for inserting and withdrawing coiled tubing from pipe to avoid bending or twisting of the coiled tubing at great distances downhole. There is provided a thruster pig that utilizes pressure differential across the thruster pig to generate force needed to inject the tubing down the pipeline. The pig includes one or more chevrons to impede fluid flow around the pig, so the pig can be pressured at its rear to move down the pipeline. There is provided an opening for allowing fluids pumped down the center of the tubing to pass to the front of the pig. There is further provided one or more valves in series or in parallel that slow the fluids to pass through the pig to the annulus behind the pig. There are a second set of check valves for allowing fluids under some conditions to flow from the annulus between the tubing and the interior surface of the pig to the front of the pig. These valves are limits of the pressure that can be exerted against the back of the pig, and will open to allow fluid to pass, principally when the pig is being withdrawn from the pipeline. This device, although effective, cannot be operated to allow the device to continue to simultaneously move forward in the pipeline while obstructions in the pipeline are being cleaned away. Also, unlike the present invention, the fluid under pressure is being injected through the bore of the coiled tubing through a single nozzle at the forward end of the pig, which limits its movement and cleaning ability in the pipeline. Also, there is no provision in this device to allow pieces of debris to flow up to the surface behind the pig, as the pig moves forward to destroy the obstructions in the pipeline.
The apparatus of the present invention and the method of utilizing same solves problems in the art in a simple and straightforward manner. What is provided is a retrievable pig apparatus having a substantially cylindrical body portion, the body portion having a central flow bore therethrough. The rear of the body portion would be secured to the first end of a length of coil tubing and would include a central fluid flow bore in fluid communication with the interior bore of the coiled tubing. There is further provided a plurality of flow bores spaced equally apart within the body, with the flow bores allowing fluid flow to be injected at a certain predetermined pressure through the flow bores, so as to be emitted on the front end of the pig for defining a high pressure spray of fluid or the like material to break up blockages in the pipeline such as paraffin or the like. The debris which is formed from the breakup of the paraffin or the like would be retrieved through the central bore back into the coil tubing to be stored in a tank or the like on the surface. There is further included a plurality of flexible cups, which are spaced apart along the outer wall of the pig body, and each of a diameter equal to the interior diameter of the pipeline, each cup secured to an interior metallic ring which is slidably engaged around the body of the pig, with the flexible cups extending a distance out from the body of the pig and the ends of which making contact with the wall of the pipeline so as to provide a continuous fluid seal between the wall of the pipeline and the ends of the plurality of flexible cups. Intermediate use of the cup there is provided a compressible safety ring, so that should the pig encounter pressures to the point which may result in the rupture of the pipeline, the compressible members will compress thus allowing the fluid to flow past the plurality of flexible cups, reducing the pressure in the pipeline. Further there is provided within the plurality of six flow bores around the interior flow bore, a system for adjusting the force that is allowed to flow through the plurality of bores in either direction by providing a first and second spring member within the bores, each of the spring members having a pre-determined compressible force for allowing the spring to be compressed and effecting fluid flow therethrough and compressed. There is further provided a means on the rear portion of the pig for allowing a fishing tool to be secured onto the pig in order to remove the pig from the pipeline in the event the pig becomes stuck within the pipeline. When this is done, fluid flow is then allowed to flow in the opposite direction within the bores, thus allowing the pig to be removed from the pipeline during use. As will be seen from the following Objects of the Invention, this improved thruster pig has many attributes which are improvements from the thruster pig disclosed in U.S. Pat. No. 6,315,498, as referred to earlier.
It is a principal object of the present invention to provide a bi-directional thruster pig apparatus, capable of attaching to a continuous coiled tubing and pull the coiled tubing a distance down a well, pipeline, or drill hole for a distance of ten miles or greater;
It is a further object of the present invention to provide a safety collapse system comprising a UMHW armature support system on each cup designed to compress and allow the cups to collapse when excessive pressure is applied, which can be predetermined to prevent any over pressure of the annulus;
It is a further object of the present invention to provide a bi-directional thrust system comprising changeable, adjustable check valves that are double acting in each direction, the amount of hydraulic thrust pressure being set and predetermined prior to the job or changed in the fields;
It is a further object of the present invention to provide a plurality of double acting check valves in the xe2x80x9ccoiltacxe2x80x9d thruster pig which would allow thrusting the coil tubing down a pipeline, hole or well at distances greater than 10 miles while washing out in front of the thruster as it moves ahead and behind it while pulling the thruster out of the pipeline, well or hole;
It is a further object of the present invention to provide double acting check valve system within the thruster pig which would allow to spray chemicals in front of the thruster pig down the coil tubing or when returning back through the pig up the annulus side, which is more economical and faster than pumping chemicals down the annulus side;
It is a further object of the present invention to provide thruster pig which allows setting the return flow check valve in the thruster to pre-set hydraulic thruster force that will help to thrust the coil tubing or pipe back down the line, thus eliminating most of the cat head or key seating frictional drag back through a radius;
It is a further object of the present invention to eliminate not only the helical bucking of the coil tubing or pipe as it is propelled down the line but also prevent yielding of the coil tubing or pipe as the thrust pressure is safely set before the jobs using the mechanical intelligence of the check valve settings;
It is a further object of the present invention to provide a thruster pig which has no metal parts that can be broken off or lost in the well or line;
It is a further object of the present invention to provide a thruster pig which can be completely dressed out and rebuilt in the field if necessary, with all double acting check valves and the collapse system being changed out, rebuilt or reset in the field;
It is a further object of the present invention to provide three or more flexible cups which can be added to the system to insure better wear for long distance runs down the pipeline well;
It is a further object of the present invention to provide a new thruster pig which may include an internal built in profile for releasing from the pig and fishing it from the line;
It is a further object of the present invention to provide a new thruster pig system which can be as short as 12 inches and still maintain thruster power to propel the coil tubing or pipe up to and beyond ten miles, while allowing the system to work through a short bend radius including but not limited to a 5D radius;
It is a further object of the present invention to provide a system that can use cups or tapered or bi-directional thrusters;
It is a further object of the present invention to provide the special molded cups designed for the thruster which can be dressed out to service a plurality of pipe sizes, for example, 6xe2x80x3, 8xe2x80x3, 10xe2x80x3 and 12xe2x80x3 and other sizes;
It is a further object of the present invention to provide a thruster pig which can generate hydraulic forces great enough to propel the coil tubing or pipe down a well a greater distance than ten miles as required and can be utilized with or without skates.
It is a further object of the present invention to provide a bi-directional thruster pig apparatus, which would allow fluid flow through the pig in two directions simultaneously, for allowing the pig to move forward within the pipeline or to be retrieved from the pipeline as the case may be;
It is a further object-of the present invention to provide a thruster pig apparatus having a compression safety release system, for allowing pressure buildup within the pipeline to compress a portion of the pig and to relieve the pressure within the pipeline;
It is a further object of the present invention to provide a thruster pig apparatus, having a plurality of outer flow channels for allowing fluid flow to flow under pressure out of the front portion of the pig and having a central flow bore for allowing the fluid flow to return rearwardly through the pig into a coil tubing and stored in a tank above ground;
It is a further object of the present invention to provide a thruster pig apparatus attached to the end of coil tubing which through a method of pushing the pig through the pipeline via pressure at the rear of the pig allows the pig to carry the coil tubing along the pipeline for distances greater than ten miles yet eliminate buckling or coiling in the coil tubing during use.